Battery formation method

Abstract

In order to solve the problem that an abnormal battery cannot be rapidly detected in the prior art, the invention provides a battery formation method which comprises the following steps: S1, after liquid injection of the battery, placing the battery for a first preset time; s2, charging the battery in the S1 at a constant current of 0.1-0.5 C to 3.4-4.4 V, and charging for 3-30 minutes; s3, placing the battery in the step S2 for a second preset time; s4, charging the battery in the step S3 to 3.7-4.4 V at a constant current of 0.5-2C for 20-80 minutes; s5, placing the battery in the step S4 for a third preset time; s6, charging the battery in the step S5 to 3.7-4.4 V at a constant current of 0.5-2C; s7, placing the battery in the step S6 for a fourth preset time; s8, the battery in the S7 is charged to 3.7-4.4 V at the constant current and constant voltage of 0.1-1 C, and the cut-off current is 0.1-1 C; and S9, placing the battery in the step S8 for a fifth preset time, and completing formation. According to the formation method provided by the invention, batch low-voltage batteries can be detected, the effect of rapidly detecting abnormal batteries is achieved, and the quality stability of battery products is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery testing, and particularly relates to a battery formation method. Background Art

[0002] There are many processes that affect the performance of lithium-ion batteries, and there are also many factors affecting performance in each process. In the industry, capacity testing and OCV testing are usually used to pick out batteries with NG capacity, NG voltage, and NG internal resistance. The production time of the battery from the mixing-OCV process is about 7-12 days. If the performance defects (such as low voltage and large internal resistance) generated in the injection process are not discovered and picked out until the OCV test, then from injection to OCV, processes such as standing after injection, formation, second sealing, cutting, folding, ironing, grading, and aging are required. Continuous production during the interval period of the processes will result in a batch of NG batteries, causing huge losses.

[0003] The AC internal resistance can only be measured after the battery is injected. If this process is added, 100% internal resistance measurement is required. This test requires an additional process and investment in human and equipment resources, increasing the battery manufacturing cost; high-temperature or normal-temperature standing after injection usually does not perform battery voltage and internal resistance tests. Therefore, the first process after standing after injection is formation, and it is the fastest method to identify during the formation process. However, 100% voltage cabinet inspection can be performed during formation, but internal resistance testing cannot be performed.

[0004] In summary, there are many deficiencies in the existing related processes and methods for battery performance detection during the battery production process. It is difficult to efficiently and low-costly detect and solve the battery performance defects generated in the injection process in the early stage. There is an urgent need for a more optimized battery performance detection and defect control scheme to improve this situation. Summary of the Invention

[0005] Aiming at the problem that the existing technology cannot quickly detect abnormal batteries during the battery production process, a battery formation method is provided.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows: The present invention provides a battery formation method, including the following operations: S1: After the battery is injected, it is left to stand for a first preset time; S2: Take the battery in S1 and charge it at a constant current of 0.1-0.5C to 3.4-4.4V for 3-30 minutes; S3: Take the battery in S2 and leave it to stand for a second preset time; S4: Take the battery in S3 and charge it at a constant current of 0.5C-2C to 3.7-4.4V for 20-80 minutes; S5: Take the battery in S4 and leave it to stand for a third preset time; S6: Take the battery in S5 and charge it at a constant current of 0.5C - 2C until it reaches 3.7 - 4.4V; S7: Take the battery in S6 and set it aside for the fourth preset time; S8: Take the battery in S7 and charge it at a constant current and constant voltage of 0.1 - 1C until it reaches 3.7 - 4.4V, with a cut-off current of 0.1 - 1C; S9: Take the battery in S8 and set it aside for the fifth preset time, and the formation is completed.

[0007] Optionally, the battery is selected from one of lithium-ion batteries, lithium-sulfur batteries, and solid-state batteries.

[0008] Optionally, the battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode active material, and the negative electrode includes a negative electrode active material; The positive electrode active material is selected from one or more of lithium cobaltate, ternary, and lithium manganate, and the negative electrode active material is selected from one or more of natural graphite and artificial graphite.

[0009] Optionally, the temperature for battery formation is 55 - 85°C, and the formation pressure is 0.5 - 1.5 MPa.

[0010] Optionally, the first preset time is 1 - 10 min.

[0011] Optionally, the second preset time is 3 - 30 min.

[0012] Optionally, the third preset time is 1 - 10 min.

[0013] Optionally, the fourth preset time is 30 - 90 min.

[0014] Optionally, the fifth preset time is 1 - 10 min.

[0015] Optionally, the constant current charging time in S6 is 10 - 60 min; the constant current charging time in S8 is 20 - 100 min for charging.

[0016] The beneficial effects of the present invention are as follows: In the battery formation method provided by the present invention, the operation in S6 is used to initially screen the battery. At this time, for abnormal batteries, due to their large internal resistance, they can reach the cut-off voltage within a short time in S6, but their capacitance is low. Therefore, after being set aside for the fourth preset time in S7, the voltage of abnormal batteries drops rapidly, and then in the operation of small current and short time charging in S8, abnormal batteries cannot be fully charged; that is, S6 utilizes the characteristic that the constant current charging time of batteries with large internal resistance is short, combined with the situation of batch low voltage during charging in the operation of S8, to be able to detect batch low voltage batteries through the formation cabinet, thereby realizing the rapid detection of batteries with abnormal internal resistance, and further helping to timely discover potential battery quality problems in the formation process and ensuring the quality stability of battery products. Brief Description of the Drawings

[0017] Figure 1 is the formation curve of a qualified battery provided by an embodiment of the present invention; Figure 2 is the formation curve of an abnormal battery provided by an embodiment of the present invention; Figure 3 is the detection result of the charging duration of a qualified battery and an abnormal battery provided by an embodiment of the present invention; Figure 4 is the detection result of the internal resistance of an abnormal battery provided by an embodiment of the present invention. Detailed Description of the Invention

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] The present invention provides a battery formation method, including the following operations: S1: After the battery is filled with liquid, it is left to stand for a first preset time; S2: Take the battery in S1 and charge it at a constant current of 0.1 - 0.5C to 3.4 - 4.4V for 3 - 30 minutes; S3: Take the battery in S2 and leave it to stand for a second preset time; S4: Take the battery in S3 and charge it at a constant current of 0.5 - 2C to 3.7 - 4.4V for 20 - 80 minutes; S5: Take the battery in S4 and leave it to stand for a third preset time; S6: Take the battery in S5 and charge it at a constant current of 0.5 - 2C to 3.7 - 4.4V; S7: Take the battery in S6 and leave it to stand for a fourth preset time; S8: Take the battery in S7 and charge it at a constant current of 0.1 - 1C to 3.7 - 4.4V, and the cut-off current is 0.1 - 1C; S9: Take the battery in S8 and leave it to stand for a fifth preset time, and the formation is completed.

[0020] Specifically, in the battery formation method provided by the present invention, the battery is preliminarily screened by the operation of S6. At this time, due to the large internal resistance of the abnormal battery, it can reach the cut-off voltage within a short time in S6. However, its capacitance is low. Therefore, after being left for the fourth preset time in S7, the voltage of the abnormal battery drops rapidly. Then, in the operation of charging with a small current and for a short time in S8, the abnormal battery cannot be fully charged. That is, in the operation of S6, by utilizing the characteristic that the constant-current charging time of the battery with a large internal resistance is short, combined with the situation of a batch of low voltages occurring during charging in S8, a batch of low-voltage batteries can be detected through the formation cabinet, thereby realizing the rapid detection of batteries with abnormal internal resistance, and further helping to timely discover potential battery quality problems in the formation process and ensuring the quality stability of battery products.

[0021] In some embodiments, the battery is selected from one of power batteries, energy storage batteries, and consumer batteries.

[0022] In some embodiments, the battery is selected from one of lithium-ion batteries, lithium-sulfur batteries, and solid-state batteries.

[0023] Specifically, the battery formation method provided by the present application is applicable to various types of batteries, such as any one of the lithium-ion batteries, lithium-sulfur batteries, and solid-state batteries described above.

[0024] In some embodiments, the battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode active material, and the negative electrode includes a negative electrode active material; The positive electrode active material is selected from one or more of lithium cobaltate, ternary, and lithium manganate, and the negative electrode active material is selected from one or more of natural graphite and artificial graphite.

[0025] In some embodiments, the temperature of battery formation is 55 - 85 °C, and the formation pressure is 0.5 - 1.5 MPa.

[0026] Specifically, in the formation method provided by the present application, the battery is formed in an environment with a temperature of 55 - 85 °C and a pressure of 0.5 - 1.5 MPa. Within this temperature range, the viscosity of the electrolyte is moderate, which will neither affect ion migration due to too low a temperature nor cause abnormal situations such as decomposition due to too high a temperature, ensuring that during the formation process, the electrolyte can continuously and stably provide a good channel for ion transport and maintain the normal and orderly progress of the electrochemical reaction inside the battery. The formation pressure is between 0.5 - 1.5 MPa. Under this pressure, the contact between the various components inside the battery is optimized, and components such as the electrode and the separator, and the electrode and the battery housing can be closely attached, which is beneficial to reducing the contact resistance inside the battery. When the contact resistance decreases, the charging current during the formation process can pass through each part of the battery more evenly and smoothly, avoiding problems such as overheating and local overcharging caused by poor local contact, and helping to improve the charge and discharge consistency and overall performance of the battery.

[0027] In some embodiments, the first preset time is 1 - 10 min.

[0028] Specifically, in a preferred embodiment, the first preset time is 4 min, that is, the time for the battery to be placed in the high-temperature and high-pressure fixture after standing at room temperature and high temperature after liquid injection is 4 min; Since after the battery is injected with liquid, the electrolyte needs to penetrate into the electrode material and the pores of the separator. The electrode material has a certain pore structure. Only when the electrolyte fully wets the electrode and the separator can ions migrate smoothly between the electrode and the electrolyte. Therefore, the battery is placed at room temperature and high temperature after liquid injection; the time for placing in the high-temperature and high-pressure fixture is 4 min, which is used to heat the battery to a set temperature, such as 80 °C, to increase the conductivity of the electrolyte so that the battery can withstand large-current charging (such as a current of 0.1C - 2C).

[0029] In some embodiments, in the formation method provided in the present application, the constant-current charging time of S6 is based on the time point corresponding to when the actual average cut-off voltage is reached; through previous tests in the present application, it is obtained that when the battery is charged at a constant current of 1C to 4.1V, the charging time of a non-abnormal battery is 20 min.

[0030] In some embodiments, the second preset time is 3 - 30 min.

[0031] Specifically, due to the charging process in the S2 operation, the electrolyte composition, ion concentration, and electrochemical state of the electrode material inside the battery have all changed. Performing the second preset time of standing in S3 again can redistribute various substances inside the battery to reach a relatively balanced state.

[0032] Specifically, in a preferred embodiment, the second preset time is 3 min.

[0033] In some embodiments, the third preset time is 1 - 10 min.

[0034] Specifically, after the constant-current charging in S4, the chemical reaction inside the battery is relatively intense, the battery temperature may rise, and the structure and state of the electrode material will also change to a certain extent. Therefore, performing the third preset time of standing can cool the battery, stabilize the structure of the electrode material to a certain extent, avoid affecting the subsequent charging process due to too high temperature or unstable structure, and at the same time, can also make the electrochemical process inside the battery reach a new balance, such as the redistribution of ion concentration in the electrolyte, to ensure the stability of battery performance.

[0035] Specifically, in a preferred embodiment, the third preset time is 2 min.

[0036] In some embodiments, the fourth preset time is 30 - 90 min.

[0037] Specifically, after the battery is charged at a constant current of 1C to 4.1V again, relatively strong electrochemical changes occur inside the battery, and it is left to stand for the fourth preset time to restore the stability of the battery performance.

[0038] Specifically, in a preferred embodiment, the fourth preset time is 30 min.

[0039] In some embodiments, the fifth preset time is 1 - 10 min.

[0040] Specifically, in a preferred embodiment, the fifth preset time is 2 min.

[0041] Under the condition of constant current charging, with the same current, the greater the internal resistance of the battery, the faster its voltage rises during charging, the shorter the charging time, and the lower the capacitance, resulting in a relatively fast voltage drop when the battery is left to stand. Therefore, S6 utilizes the characteristic that the constant current charging time of a battery with a large internal resistance is short, combined with subsequent operations, to test the resistance of the test battery. Combining the screening mechanism (the situation of abnormal batteries with low voltage and large internal resistance), it can be detected according to the formation method, which helps to timely discover potential battery quality problems in the formation process and ensure the quality stability of battery products.

[0042] In some embodiments, the constant current charging time in S6 is 10 - 60 min; the constant current charging time in S8 is 20 - 100 min for charging.

[0043] Specifically, from the perspective of screening abnormal batteries, S6 makes a preliminary discrimination by utilizing the characteristic that the constant current charging time of a battery with a large internal resistance is short. If the charging time is too short, it may cause the normal battery to end this step before being fully charged, affecting the accurate judgment of the overall performance of the battery in the subsequent process; while if the charging time is too long, exceeding 60 minutes, the difference in charging duration between abnormal batteries and normal batteries may become less obvious, which is not conducive to accurately screening out batteries with abnormal internal resistance.

[0044] In step S8, by combining the characteristic that abnormal batteries cannot be fully charged, by reasonably setting the time range of 20 - 100 min, it is more conducive to accurately distinguishing normal batteries and abnormal batteries. If the time range is too narrow, it may cause some normal batteries to be misjudged as abnormal batteries due to insufficient charging time, or the distinguishability between abnormal batteries and normal batteries is not enough, affecting the accurate control of battery quality.

[0045] The present invention will be further described below through embodiments.

[0046] Embodiment 1 This embodiment is used to illustrate a battery formation method disclosed by the present invention, including the following operating steps: S1: After the battery is filled with liquid and infiltrated, it is placed on the formation machine for 4 minutes; S2: Take the battery in S1 and charge it at a constant current of 0.5C to 3.7V for 6 minutes; S3: Take the battery in S2 and place it for 3 minutes; S4: Take the battery in S3 and charge it at a constant current of 1C to 4.1V for 40 minutes; S5: Take the battery in S4 and place it for 2 minutes; S6: Take the battery in S5 and charge it at a constant current of 1C to 4.1V; S7: Take the battery in S6 and place it for 30 minutes; S8: Take the battery in S7 and charge it at a constant current of 0.2C to 4.0V, and stop when the charging current is 0.1C; S9: Take the battery in S8 and place it for 2 minutes; S10: Take the battery in S9 and perform OCV test detection.

[0047] Use the formation cabinet software with high-temperature and high-pressure fixtures to screen the constant current time for the S6 step. The constant current charging time ≥ 20 minutes is a qualified product, and the constant current charging time < 20 minutes is an NG product. The equipment automatically picks out the NG product batteries; then, through the S8 step, voltage screening is performed. The voltage ≥ 3.955V is a qualified product, and the voltage < 3.955V is an NG product. The equipment automatically picks out the NG product batteries.

[0048] Perform relevant performance tests on the obtained Example 1 above: Voltage test: Use an internal resistance test instrument (such as the HIOKI BT3562 model instrument) for testing. For example, the voltage of the NG battery is 3.9352V, and the voltage of the OK battery is 3.9983V; Internal resistance test: Use an internal resistance test instrument (such as the HIOKI BT3562 model instrument) for testing. For example, the internal resistance of the NG battery is 103 mΩ, and the internal resistance of the OK battery is 84 mΩ.

[0049] As Figure 1-2 described, Figure 1 is the formation curve graph of the qualified battery, Figure 2 is the formation curve of the abnormal battery, Figure 1 and Figure 2By comparison, it can be seen that in the constant current charging operation of the screening method S6 provided in this application, the time for the average voltage of the qualified battery to reach 4.1V is 20 minutes, and its internal resistance is 84 mΩ. In the constant current charging operation of the screening method S6 provided in this application, the time for the average voltage of the NG battery to reach 4.1V is 10.2 minutes, and its internal resistance is 99 mΩ. From the above test results, it can be seen that during the constant current charging process of the abnormal (NG) battery, due to its large internal resistance, the voltage rises rapidly. Therefore, the cut-off voltage can be reached in a short time during the constant current charging, while the voltage of the qualified battery rises slowly during the charging process. Under the same constant current charging conditions, the charging time required for the qualified battery is much longer than that of the NG battery.

[0050] From Figure 3 the test results, it can be seen that in the constant current charging operation of S6, the charging time used by the NG battery with a NG formation cabinet inspection voltage is 9.8 minutes less than that of the battery with a qualified formation cabinet inspection voltage. Figure 3 The test results Figure 1 further illustrate that the NG battery can reach the corresponding voltage in a short time, corresponding to Figure 2 the test results; Figure 4 In Figure 4 the internal resistance of the batch of low-voltage batteries detected by the formation cabinet was detected. From

[0051] Combining Figures 1-4 the test results, it can be seen that in the battery formation method provided by the present invention, the operation of S6 utilizes the characteristic that the constant current charging time of the battery with a large internal resistance is short, combined with the situation of batch low voltage occurring during the charging in the operation of S8, to be able to detect the batch of low-voltage batteries through the formation cabinet, thereby realizing the rapid detection of batteries with abnormal internal resistance, and further helping to timely discover potential battery quality problems in the formation process.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A battery formation method, characterized in that, Including the following operations: S1: After the battery is filled with liquid, it is left to stand for the first preset time; S2: Take the battery in S1 and charge it at a constant current of 0.1 - 0.5C to 3.4 - 4.4V for 3 - 30 minutes; S3: Take the battery in S2 and leave it to stand for the second preset time; S4: Take the battery in S3 and charge it at a constant current of 0.5C - 2C to 3.7 - 4.4V for 20 - 80 minutes; S5: Take the battery in S4 and leave it to stand for the third preset time; S6: Take the battery in S5 and charge it at a constant current of 0.5C - 2C to 3.7 - 4.4V; S7: Take the battery in S6 and leave it to stand for the fourth preset time; S8: Take the battery in S7 and charge it at a constant current and constant voltage of 0.1 - 1C to 3.7 - 4.4V, with a cut-off current of 0.1 - 1C; S9: Take the battery in S8 and leave it to stand for the fifth preset time, and the formation is completed.

2. The battery formation method according to claim 1, wherein The battery is selected from one of lithium-ion batteries, lithium-sulfur batteries, and solid-state batteries.

3. A battery formation method according to claim 1, characterized in that, The battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode active material, and the negative electrode includes a negative electrode active material; The positive electrode active material is selected from one or more of lithium cobaltate, ternary, and lithium manganate, and the negative electrode active material is selected from one or more of natural graphite and artificial graphite.

4. A battery formation method according to claim 1, characterized in that, The temperature for battery formation is 55 - 85°C, and the formation pressure is 0.5 - 1.5 MPa.

5. A battery formation method according to claim 1, characterized in that, The first preset time is 1 - 10 minutes.

6. The battery formation method according to claim 1, characterized in that The second preset time is 3 - 30 minutes.

7. A battery formation method according to claim 1, characterized in that The third preset time is 1 - 10 minutes.

8. A battery formation method according to claim 1, characterized in that, The fourth preset time is 30 - 90 minutes.

9. A battery formation method according to claim 1, characterized in that, The fifth preset time is 1 - 10 minutes.

10. A battery formation method according to claim 1, characterized in that, The constant current charging time in S6 is 10 - 60 minutes; the constant current charging time in S8 is 20 - 100 minutes for charging.

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